"They're not in my mind," the ex-NFL star says of the UFC heavyweight beasts ... "They're in my sights, brother. They're locked in."

Of course, Hardy ain't sure exactly when those fights will go down ... he tells TMZ Sports, after being DQ'd in his first-ever UFC fight -- he's got a lot to learn before he steps in the Octagon with the superstars.

But, he says guys like Stipe and The Black Beast are still the goal ... telling us, "When I go there and I do fight these guys -- hopefully soon enough when I do elevate and graduate -- it's going to be Goliath vs. Goliath."

Hardy's first step in that plan? A bout with Dmitrii Smoliakov in the co-main event of Saturday night's ESPN+ Fight Night 150.

Greg says he's more prepared for this UFC tilt than his first one -- the one he lost after he illegally kneed Allen Crowder back in January.

Hardy tells us he was "overwhelmed" by the stage in that fight ... but he's learned from it -- and says he's ready to kick some ass Saturday!!!